A Complete Guide to Choosing the Right Gas Boiler

Choosing the right gas boiler is one of the most important home improvement decisions you'll make. The right boiler not only keeps your home warm and comfortable but can also significantly impact your energy bills and carbon footprint. This comprehensive guide will walk you through everything you need to consider when selecting a new gas boiler for your Irish home.

Why Boiler Choice Matters

Your boiler accounts for approximately 60% of your home's annual energy costs. With rising energy prices, an efficient boiler can save you hundreds of euros each year. Additionally, a well-matched boiler improves comfort, reduces environmental impact, and provides reliable heating and hot water for 10-15 years.

Types of Gas Boilers

There are three main types of gas boilers available in Ireland:

1. Combi (Combination) Boilers

How they work: Combi boilers heat water directly from the mains when you turn on a tap, eliminating the need for a hot water storage cylinder or cold water tank.

Best suited for: Small to medium-sized homes with limited space and 1-2 bathrooms.

Advantages:

• Space-saving (no need for water tanks or cylinders)
• Hot water on demand
• Energy efficient as water is heated only when needed
• Lower installation costs
• Good water pressure if your mains pressure is good

Disadvantages:

• Performance can decrease if multiple taps/showers are used simultaneously
• Not ideal for homes with high hot water demand
• Dependent on mains water pressure
• Cannot work with solar thermal systems without additional equipment

2. System Boilers

How they work: System boilers heat water that is stored in a hot water cylinder. Most components are built into the boiler, making installation simpler.

Best suited for: Medium to large homes with multiple bathrooms or high hot water demand.

Advantages:

• Can supply hot water to multiple taps simultaneously
• Compatible with solar thermal systems
• No need for a cold water tank in the attic
• Consistent water pressure regardless of mains pressure
• Components are built into the boiler unit

Disadvantages:

• Requires space for a hot water cylinder
• Hot water can run out and need time to reheat
• Higher installation costs than combi boilers
• Energy is used to keep water hot even when not needed

3. Conventional (Regular) Boilers

How they work: Conventional boilers heat water that is stored in a hot water cylinder and typically work with a cold water storage tank in the attic.

Best suited for: Older properties with existing traditional heating systems or very large homes with multiple bathrooms.

Advantages:

• Can supply hot water to multiple taps simultaneously
• Works well in areas with low water pressure
• Compatible with solar thermal systems
• Often the easiest/cheapest option when replacing an existing conventional system

Disadvantages:

• Requires space for both a hot water cylinder and cold water tank
• More complex installation
• Hot water can run out and need time to reheat
• Energy is used to keep water hot even when not needed

Sizing Your Boiler Correctly

Getting the right size (output) boiler is crucial. An undersized boiler won't meet your heating and hot water needs, while an oversized boiler wastes energy and money.

Factors Affecting Boiler Size

• Home size: Larger homes generally require higher-output boilers
• Insulation level: Well-insulated homes need less heating power
• Number of radiators: More radiators require more heating capacity
• Number of bathrooms: More bathrooms mean higher hot water demand
• Household size: More occupants typically mean more hot water usage

Rough Sizing Guide

While professional sizing is recommended, here's a general guideline for combi boilers:

• 24-27kW: Apartments or small houses (1-2 bedrooms, 1 bathroom)
• 28-34kW: Medium houses (3 bedrooms, 1-2 bathrooms)
• 35-42kW: Larger houses (4+ bedrooms, 2+ bathrooms)

For system and conventional boilers, heating output and hot water output are specified separately, typically requiring 12-15kW for heating plus additional capacity for hot water.

Important: A qualified heating engineer should perform a heat loss calculation on your home to determine the exact size needed.

Energy Efficiency Considerations

All new gas boilers sold in Ireland must be high-efficiency condensing models, which typically have efficiency ratings of 90% or higher. However, efficiency still varies between models.

Efficiency Ratings

Look for the EU energy label and ErP (Energy-related Products) efficiency rating:

• A-rated boilers are the most efficient (90%+)
• Higher efficiency = lower running costs and lower carbon emissions
• Some modern boilers achieve efficiency ratings of 94% or higher

Advanced Efficiency Features

• Weather compensation: Adjusts boiler temperature based on outdoor conditions
• Load compensation: Varies flow temperature based on the heating demand
• Smart controls: Learn your schedule and optimize heating accordingly
• Modulation range: Wider ranges allow the boiler to run at lower outputs when less heat is needed

Controls and Smart Features

Modern boiler controls can significantly improve both comfort and efficiency:

Basic Controls

• Programmer/timer: Sets when the heating and hot water turn on and off
• Room thermostat: Maintains your desired room temperature
• Thermostatic radiator valves (TRVs): Control temperature in individual rooms
• Cylinder thermostat: Regulates hot water temperature (for system and conventional boilers)

Advanced Controls

• Smart thermostats: Allow remote control via smartphone apps
• Zoned heating: Control different areas of your home independently
• Learning thermostats: Adapt to your routines and preferences
• OpenTherm: Allows communication between compatible boilers and thermostats for more precise control

The SEAI offers grants for certain heating controls upgrades when installed alongside a new boiler.

Installation Considerations

Proper installation is just as important as choosing the right boiler:

Boiler Location

• Ideally positioned on an exterior wall for flue venting
• Consider noise levels if positioning near bedrooms
• Accessibility for servicing and maintenance
• Proximity to gas supply and water mains (for combi boilers)

Flue Requirements

• Flues must terminate in a safe location outside
• Specific distance requirements from windows, doors, and boundaries
• Horizontal, vertical, or concentric flue options depending on your property

System Cleansing

When installing a new boiler, it's essential to:

• Power flush the existing system to remove sludge and debris
• Install a magnetic filter to capture future contaminants
• Add inhibitor chemicals to prevent corrosion

Legal Requirements

• Installation must be carried out by an RGII-registered gas installer
• The installer must provide a Declaration of Conformance certificate
• Building regulations compliance, particularly for flue positioning

Cost Considerations

When evaluating boiler costs, consider both upfront and long-term expenses:

Initial Costs

• Boiler unit: €1,000-€3,500 depending on type, size, and brand
• Installation: €800-€1,500 depending on complexity
• System upgrades: Potentially €500-€1,500 for new radiators, pipes, controls, etc.

Operating Costs

• Higher efficiency ratings = lower running costs
• Smart controls can reduce consumption by 15-20%
• Annual servicing costs (approximately €80-€120)

Available Grants

The SEAI offers grants for energy efficiency improvements including:

• Heating controls upgrades (when installed with a new boiler)
• Additional grants for overall home energy upgrades

Reliability and Warranty

A boiler is a long-term investment, so reliability matters:

• Warranty length: Most manufacturers offer 5-10 year warranties, with longer warranties generally indicating higher confidence in reliability
• Manufacturer reputation: Research brands for reliability track records
• Parts availability: Mainstream brands typically have better parts availability
• Service networks: Consider the availability of qualified technicians for your chosen brand

Extended warranties usually require annual servicing by qualified engineers.

Future-Proofing Your Heating System

As Ireland transitions to a low-carbon future, consider how your heating system might adapt:

• Hydrogen-ready boilers: Some modern boilers are designed to work with hydrogen blends, potentially extending their lifespan as gas supplies change
• Hybrid systems: Consider boilers that can work alongside heat pumps for a staged transition
• Compatibility with renewable systems: System and conventional boilers can often work with solar thermal systems

Making Your Final Decision

To summarize the selection process:

1. Determine your boiler type based on your property size, hot water needs, and space constraints
2. Calculate the correct size with help from a qualified heating engineer
3. Compare efficiency ratings and potential running costs
4. Consider control options that will optimize both comfort and efficiency
5. Evaluate warranties and reliability of different brands
6. Get multiple quotes from RGII-registered installers
7. Check for available grants through the SEAI

Conclusion

Choosing the right gas boiler is a significant decision that impacts your comfort, energy bills, and environmental footprint for years to come. By understanding the different types, sizing requirements, efficiency features, and control options, you can make an informed choice that best suits your home and budget.

At EmeraldGas, our RGII-registered engineers can provide expert advice on selecting and installing the perfect gas boiler for your Irish home. We offer free, no-obligation consultations to assess your heating needs and recommend the most suitable options.